Rotating an object between two positions??

How can i rotate an object to change the Z value in two ways: posA=rotation(0,0,0) posB=rotation(0,0,180); So yeah , i want to my object rotate each time a Input of Mouse0 is recieved(Not until it reaches posA/B) I tried with transform.rotate but this gives no sense of movement and Lerps are not quite clear . Do you mind sharing your knowledge? Thanks!